Life on Mars

On August 6, 1996, Nasa announced the discovery of evidence for the existence of fossil life on Mars.

Scientists of Nasa and Stanford University (California) have found evidence for fossil life in a Martian rock. This so-called SNC meteorite had been ejected into space by an asteroid impact on Mars about 15 million years ago, and travelled around the Sun on an elliptical orbit on its own, as a miniture planet, until it impacted in an antarctic ice field about 13,000 years ago, where it was found in 1984. It was labelled "Allen Hills 84001" or "ALH 84001".

What was discovered is complex organic compounds within the rock, so-called PAHs ("polycyclic aromatic hydrocarbons). The chemistry, mineralogy, and texture of these compounds and surrounding carbonates, collectively, point to a biological origin, and thus the conclusion that there is evidence for primitive life on Mars. This life is thought to have existed there billions of years ago (the carbonates are estimated at an age of 3.6 billion years), and consist of simple micro-organisms similar to terrestrial bacteria.

The claim of evidence for life depends on a number of facts which had to be examined:

• Evidence had to be established that the rock had its origin on Mars.
• It had to be checked if the organic compounds could have terrestrial origin (i.e. if they are contamination added during the 13,000 years when the rock was in the ice).
• If of Martian origin, investigations had to be performed if they had formed in biological or non-biological process.

Thanks to Hartmut Frommert <spider@seds.org>